Human Evolution Notes

Human Evolution

• Intro:
  • The lecture will focus on applying concepts learned to human evolution.
  • It will cover exciting tools used to understand human evolution.
  • The content is designed to be more fun and less confusing than it was in the past.
  • There will be basic questions about this content on the exam, so don't worry about understanding all the details.
  • Remember why marine inverts were discussed in the macroevolution lecture.

Lesson Objectives

• Describe human evolution across multiple scales.
• Discuss the last common ancestor with apes.
• Explain early human evolution and important phenotypic changes.
• Provide contemporary examples of humans evolving today.
• Discuss the importance of paleogenomics in understanding human evolution, particularly the assembly of the Neanderthal genome in 2010.

Humans and Chimpanzees

• Chimpanzees are our closest living relatives; we share the most recent common ancestor with them out of all the apes.
• The lecture will walk through different divergence events between early humans and modern humans.
• The dates of these divergence events are subject to change due to new fossil finds and genome sequencing.
• Humans and chimpanzees diverged from their last common ancestor about 7,000,000 years ago.
• The first primates evolved between 55,000,000 and 65,000,000 years ago.
• The extinction of the dinosaurs (about 65,000,000 years ago) led to new niches for primates to evolve into.
• Extinctions of one lineage can facilitate the adaptive radiation of another lineage.

Bias in Human Evolutionary Studies

• Human evolutionary studies are prone to bias and strong feelings because we are humans.
• There is a tendency to get lost in the idea of the "march towards progress," which is incorrect.
  • It is incorrect to assume that more recent species came directly from the species that came before them.
  • Every species comes from a common ancestor and goes on its own evolutionary journey.
• When looking at phylogenetic trees, remember that when we diverge from common ancestors, the other species are also evolving, and we did not come from them.
• The term "sister lineages" should be used instead of assuming direct ancestral relationships.
• It's easy to forget that many of these earlier species went extinct.
• Anthropologists and paleobiologists often use skulls as props when discussing human evolution.

Phylogenetic Tree and Early Human Evolution

• Phylogenetic tree showing relationships between humans, Neanderthals, Homo erectus, and earlier hominin species.
• Early in human evolution, we shared a common ancestor with chimpanzees.
• Early adaptations favored walking on two feet, not just a little bit, but actually becoming effective walkers.
• Smaller canine teeth also emerged, leading to changes in diet.
• Enlarged cheeks, jaws, and teeth facilitated differences in diet, skull shapes changed as well.
• Changes in the size of the brain are observed in early Homo species, suggesting increased cognitive abilities.
• Changes in the digestive system indicate a shift towards hunting in groups and eating meat.
• Adaptations favored walking longer distances and running more efficiently, facilitating hunting in groups.
• Larger skulls and brains are conducive to culture and social relationships.

Understanding Human Evolution

• Up until the 2000s and 2010s, understanding human evolution relied on fossils, tools, and hypotheses about behavior and movement.
• Genomic data has helped to resolve some of the confusing aspects of human evolution.

Early Hominin Species

• Evolved in Africa between 7,000,000 and 4,400,000 years ago.
• Showed differences from apes, such as bigger skulls and changes in teeth.
• Evidence of walking on two feet starts to appear in the fossil record.

Skull Size and Brain Evolution

• Skulls were used to estimate brain size.
• Brain size increased as species diverged, potentially related to more sophisticated social structures, hunting, and language evolution.
• Changes in face shape and skull structure can provide insights into language capabilities and adaptation to different environments.

Australopithecines

• Appeared in the fossil record around 4,400,000 to 1,400,000 years ago.
• Seem to be fully walking upright.
• Finding fossils of Australopithecus (e.g., "Lucy") helped us understand human evolution.
• Early humans could run long distances, which is important for migratory patterns.
• Differences in rib cage structure indicate changes in diet from plants to meat and energy-rich tubers.
• Energy saved from not climbing trees could be allocated to brain development.
• Many human species coexisted at the same time, indicating branching evolutionary paths rather than a linear progression.

First Homo Species

• Evolved in Africa about 2,000,000 years ago.
• Homo erectus is one of the oldest and longest-lived Homo species (lived for 2,000,000 years).
• Homo erectus is important for understanding migratory patterns.
• Skulls of Homo erectus looked more like human skulls.

Homo Erectus

• The first Homo species to leave Africa.
• Evidence of Homo erectus is found in Africa and other parts of the world, showing that walking on two feet facilitated migration.
• Early humans worked together, had sophisticated social structures, and hunted in groups.
• Skull changes, such as smaller incisors and canines and flatter molars with less enamel, indicate a shift from tougher fruits and plants to seeds, nuts, and meats.
  *_ The lack of enamel can show that these populations shifted from fruits and plants to nuts and meats.

Migration

• Homo erectus left Africa about 2,000,000 to 1,800,000 years ago and spread throughout Asia.
• Neanderthals evolved in Western and Central Eurasia and were never in Africa.
• Homo sapiens overlapped with Neanderthals and Homo erectus in Europe and Asia.
• Denisovans were discovered in the Himalayan Plateau and are considered a sister group to the Neanderthals.

Homo Neanderthalis

• They evolved from 400,000 years to 30,000 years ago and evolved in Eurasia
• They branched from Homo Erectus in Europe.
• Neanderthals were located in Germany.

Out of Africa

• Homo erectus left Africa about 2,000,000 years ago.
• Modern Humans evolved from Erectus
• Homo sapiens evolved from Erectus in Africa.
• There is no Neanderthal DNA in Modern Humans who evolved out of Africa but there is for those who evolved outside of it.

Neanderthal Genome

• The first draft genome of the Neanderthals happened in 2010.
• Savante Pabo was a scientist at the Max Planck Institute.
• His research group extracted the DNA and put together a Genome from the population.

Ancient DNA

• Genomes has microbial contamination and human like genomes
• His research paved the way for Paleogenomics.
• They usually get DNA from Caves because it's well protected environmentally.
• Scientists take bones and grind them into powder to then extract DNA

Homo Sapiens, Homo Erectus and Neanderthals

• There were Homo Erectus in Africa, Europe and Asia. Homo Sapiens were only located in Africa.
• Homo Sapiens were in Ethiopia 150,000 to 200,000 years ago.
  • When they exchanged genetic material with the Neanderthals then radiated into Europe. This is why everyone outside of Africa carries the DNA.

Genetic Drift

• The greatest genetic diversity in humans comes from Africa.
• Europe and Asia has less genetic variation.
• Genetic drift also shows us that many humans were of one population coming from the same group.
• Mammels do not usually breed between themselves and only happens with those within the same species.

Comparison for Nucleotide Differences

• Researchers were able to compare Human, Neanderthal and Chimpanzee sequences
• Researchers extracted the DNA from Croatio.

Discovery of Denisovans

• Savante's research did lead to the discovery of the Denisovans in Asia.
• Researchers found the DNA in a finger that was 40,000 years old
• They found this to occur in Asia in the Tibetan Plateau
• Population split roughly 380,000 to 470,000 years ago.
• There was also some splitting between Neanderthals.

Conclusion from Modern Data

• When putting together how Humans migrated they wanted to start from a common ancestor that was earlier in its history.
• They had different DNA to compare between Haplotypes.
• There was the discovery of a Divergence with Introgression
• Modern Human had a Denisovan variant between each other.

Review of Key Points

• This was all speculation until Pavo released his research.
• He was known for his expertise on human evolution.

What Makes Humans Unique

• Humans are unique due to cultural complexity such as communication and social structure
• They have sophisticated communication and understand many more things that neanderthals did not.
• Neanderthals understood social structure on a very minute level.

Modern Day Evolution

• There is a presence of Modern DNA from Denisovan ancestry in all populations except for Africa.
• The Tibetan population have adapted over time for living in high altitudes of 4,0000 meters because their oxygen levels were 40% different.
• DNA from Cave fossils can be preserved to show these genomes.
• There was a different research group that researched at UC Berkeley about genetic differences between people who lived in the Tibetan Plateau
• There was an EPAS1 gene difference that showed genetic variation with ancestry from those that lived there.
• Researchers found that the same human DNA was not the same and the mutation occurred in one person then was spread to other regions.

Other Modern Research

• Groups of Humans living in the Andes have slightly new elevations and they also found the EPAS1 gene changed in the Population.
• The mutations found were not the same mutations.
• There was not the introgression event found in these populations.

Fat and Protein Diet

• There are humans that have Inuit ancestry with Greenland who are also very well adapted to eat foods with a high level of fat and protein.
• A study that showed this was one where their DNA had a less than 5% European ancestry and there were very strong variations in the genome of fatty acid metabolism.
• There were 3 genes found FADS1, FADS2, FADS3 genes that were involved with pathway of fatty acid synthesis.
• The pathway showed that the meat diet and marine diet have evolved in different pathways.

Review for the Exam

• There are really, really cool resources that can guide a student in learning about DNA.
• The videos that are provided explain genetic signatures to have students understand a good break down of the information.
• Definitely check out the different videos as they can really help increase retention.
• The final exam is on Friday June 6th at 8AM.
• TAs are going to start the exam and the Instructor will be in the second half of the exam.
• Calculators and rulers can be used but there will be no need for any calculations.
• Look at the study guide and the homework keys to help you understand where you will need to devote your study to.
• There is short answer portion and try to just answer with bullet points.
• Remember you can view previous lectures and remember to focus on midterm content.
• People were graded with some points off and the instructor said that they may have another opportunity to recover those points.